Plasmid DNA isolation (i.e., plasmid preps, mini-preps, rapid DNA preps, among other procedures) remains a repetitious and tedious laboratory task. Plasmid DNA isolation from bacteria has traditionally been performed using the “alkaline lysis” method, in which bacteria are resuspended in lysis buffer (P1), disrupted in a solution of NaOH and SDS (P2), neutralized in a solution containing sodium acetate (P3), and then subjected to centrifugation to sediment the flocculent cell debris containing denatured proteins and genomic DNA. Plasmid DNA remains in suspension, and is recovered by alcohol precipitation (see, e.g., Sambrook and Russell (2001) Molecular Cloning. Cold Spring Harbor Laboratory Press.).
Current popular methods of plasmid DNA preparation are based on the alkaline lysis method but use a spin-column to remove the debris from the alkaline lysate. The plasmid DNA is then recovered in a separate step, e.g., by alcohol precipitation of binding to a DNA-binding matrix. While the use of spin-column devices and kits have improved the speed and efficiency of plasmid preparation, the process continues to require multiple steps and fluid transfers. The need exists for more efficient methods, apparatus, and reagents for preparing plasmid DNA from bacteria.